A variety of apparatus for carrying out this cleaning technique have been devised in the past. The simpler systems utilize a hand-held wand with one spray nozzle and one vacuum nozzle, as disclosed in U.S. Pat. No. 4,991,254, granted to James R. and Michael J. Roden on Feb. 12, 1991, for "CLEANING SYSTEM". More complex systems may employ a motor-driven rotating head with multiple spray nozzles and multiple vacuum nozzles. An example of the latter apparatus is described in U.S. Pat. No. 4,264,999, granted May 5, 1981, to Clifford L. Monson for "ROTARY FLOORING SURFACE TREATING DEVICE". That same inventor has also proposed to equip a motor-driven, rotating head with a plurality of vacuum nozzles, each of which is rotatable about its own axis. That apparatus is disclosed in U.S. Pat. No. 4,692,959, granted Sep. 15, 1987, for "ROTARY CLEANER/SCRUBBER MECHANISM".
One undesirable operating characteristic of rotary single head cleaning devices is their tendency to veer off in different directions, depending upon the handling forces that are applied. Control of the heavy, commercial device of, say, 35 to 50 pounds, can be difficult and tiring for the operator.
Lighter weight, domestic floor polishing devices have been equipped with dual, oppositely rotating, brushes or pads to improve their handling characteristics. But the problem with dual head devices in the past has been their tendency to leave an untreated strip of surface between the two heads.
There continues to be a need for a heavy duty, commercial surface cleaning appliance which is easily controlled by the operator and which is capable of effecting uniform cleaning across a wide swath of surface.